The term, “improvisation,” is often used in colloquial speech to connote activities, actions, or plans undertaken with little or no forethought or preparation. Similar ascriptions have been applied to musical improvisation—jazz in particular—in order to suggest that improvised music lacks the technical, intellectual, and cultural complexities and refinements of traditional Western classical music. As I have argued elsewhere, I find the strict, rigid division assumed between jazz (as largely improvised music) and classical (as largely non-improvised music) to be inaccurate and misleading. There are, of course, improvisatory elements in classical music, ranging from the motif development that characterizes the compositional process to the performative variations of specific melodic lines ornamented and executed by the musicians themselves. Rather than a dichotomous view of composition and improvisation, I suggest understanding the two as occupying different “places” on a continuum and having the ability to move to a different “place” depending upon the degree of improvisatory space the particular composition or piece allows.
Having stated these initial caveats (with more to come), nonetheless, there are features that characterize jazz improvisation, distinguishing it from the common practices of Western classical composition. For example, the jazz improviser cannot take back, or as Lee B. Brown puts it, “erase,” the notes he has played in the course of his improvised solo. In contrast, in the process of working out her composition, a composer can alter a theme, as well as a rhythmic or melodic motif, or she can decide to abandon the theme altogether in favor of a new one. This antecedent compositional activity is something we, as listeners, never experience. A jazz improviser does not have this past-time luxury but must play in the moment, in time. “He can only build upon the steps he has just taken.” Brown calls this the improviser’s “situation.” This dynamic, out-in-the-open, present compositional activity in which the jazz improviser engages is, of course, risky. A player might exceed his technical abilities and thus be unable to recover from a lightening speed melodic run developed in conversation with the other musicians. Likewise, a soloist might begin a musical idea that starts off well and yet fails midway through the piece. Even so, risks and “imperfections” of this sort are, at least in part, what jazz enthusiasts appreciate, as they create an unfolding musical drama for the musicians and the audience. Stated with more specificity, because the jazz improviser always plays in real time and thus must choose to act (to choose not to play is also an act), her musical acts—failures and successes alike—become, in a very literal sense, part of the musical piece itself. As Brown puts it, in jazz improvisation, “[t]he risk-taking process itself becomes an ingredient in the result. […] With improvised music, all attempts at revision too become part of the music.”
 See, for example, Nielsen, “What Has Coltrane to Do With Mozart.” See also, Gould and Keaton, “The Essential Role of Improvisation in Musical Performance,” 143–48.
 Brown, “‘Feeling My Way’: Jazz Improvisation and Its Vicissitudes,” 114
 Ibid., 119.